VC Quirks 1

gistfile1.cpp

#include <iostream>
#include <functional>

typedef std::function<int(int)> fii;

template<typename Fn>
auto f(Fn fn)
-> typename std::enable_if<!std::is_constructible<fii, Fn>::value, int>::type
{ return 10; }

int f(fii) { return 20; }

int xx(int, int) { return 0; }

int main() {
    std::cout<< f(xx) << std::endl;
}